Class AIMDBackoffManager

java.lang.Object
org.apache.hc.client5.http.impl.classic.AbstractBackoff
org.apache.hc.client5.http.impl.classic.AIMDBackoffManager
All Implemented Interfaces:
BackoffManager
@Contract(threading=SAFE) public class AIMDBackoffManager extends AbstractBackoff

The AIMDBackoffManager applies an additive increase, multiplicative decrease (AIMD) to managing a dynamic limit to the number of connections allowed to a given host. You may want to experiment with the settings for the cooldown periods and the backoff factor to get the adaptive behavior you want.

Generally speaking, shorter cooldowns will lead to more steady-state variability but faster reaction times, while longer cooldowns will lead to more stable equilibrium behavior but slower reaction times.

Similarly, higher backoff factors promote greater utilization of available capacity at the expense of fairness among clients. Lower backoff factors allow equal distribution of capacity among clients (fairness) to happen faster, at the expense of having more server capacity unused in the short term.

Since:
4.2

  • Constructor Details

    • AIMDBackoffManager

      public AIMDBackoffManager(org.apache.hc.core5.pool.ConnPoolControl<HttpRoute> connPerRoute)
      Constructs an AIMDBackoffManager with the specified ConnPoolControl and Clock.

      This constructor is primarily used for testing purposes, allowing the injection of a custom Clock implementation.

      Parameters:
      connPerRoute - the ConnPoolControl that manages per-host routing maximums

  • Method Details

    • getBackedOffPoolSize

      protected int getBackedOffPoolSize(int curr)
      Returns the backed-off pool size based on the current pool size. The new pool size is calculated as the floor of (backoffFactor * curr).
      Specified by:
      getBackedOffPoolSize in class AbstractBackoff
      Parameters:
      curr - the current pool size
      Returns:
      the backed-off pool size, with a minimum value of 1

    • setBackoffFactor

      public void setBackoffFactor(double d)
      Sets the factor to use when backing off; the new per-host limit will be roughly the current max times this factor. Math.floor is applied in the case of non-integer outcomes to ensure we actually decrease the pool size. Pool sizes are never decreased below 1, however. Defaults to 0.5.
      Parameters:
      d - must be between 0.0 and 1.0, exclusive.